go - 责任链-当前失败时如何调用特定处理程序

Question

我要使用 Chain of responsibility pattern对于简单的 CLI 对话框:

type Handler interface {
    Request(flag bool)
}

type AskName struct {
    next Handler
}

func (h *AskName) Request(flag bool) {
    fmt.Println("AskName.Request()")
    if flag {
        h.next.Request(flag)
    }
}

type AskAge struct {
    next Handler
}

func (h *AskAge) Request(flag bool) {
    fmt.Println("AskAge.Request()")
    if flag {
        h.next.Request(flag)
    }
}

type AskEmail struct {
    next Handler
}

func (h *AskEmail) Request(flag bool) {
    fmt.Println("AskEmail.Request()")
}

func main() {
    handlerA := &AskName{&AskAge{new(AskEmail)}}
    handlerA.Request(true)
}

问题:想象一下用户输入无效电子邮件的情况。如何重新调用 AskEmail 处理程序(或调用其他处理程序)？

例如，如果我这样拆分逻辑:

type AskEmail struct {
    next Handler
}

func (h *AskEmail) Request(flag bool) {
    fmt.Println("AskEmail.Request()")
    if flag {
        h.next.Request(flag)
    }
}

type ValidateEmail struct {
    next Handler
}

func (h *ValidateEmail) Request(flag bool) {
    fmt.Println("ValidateEmail.Request()")
}

如果 ValidateEmail 失败，我如何从 ValidateEmail 调用 AskEmail？

Answer 1

我认为你可以做到这一点

type AskEmail struct {
    next Handler
}

func (h *AskEmail) Request(flag bool) {
    fmt.Println("AskEmail.Request()")
    if flag {
        h.next.Request(flag)
    }
}

type ValidateEmail struct {
    next Handler
    prev Handler
}

func (h *ValidateEmail) Request(flag bool) {
    fmt.Println("ValidateEmail.Request()")
    if !valid {
       h.prev.Request(flag)
    }
}

askEmail := &AskEmail{}
validateEmail := &ValidateEmail{prev: askEmail}
askEmail.next = validateEmail